>>33296619Generation 4, with No Guard helping Dynamic Punch and Stone Edge as well as solid bulk and a resistance to rocks. It was also really good in Generation 2 because of Cross Chop on Blissey and Snorlax, Fire Blast on Skarmory and Steelix, and Rock Slide for coverage, as well as Generation 3 because you could switch in to Will-o-Wisp from Weezing/Dusclops and get buffed in attack because Guts. It sucked in 1 because Psychic types, Generation 5 hurt it bad because of Psyshock and it having worse physical bulk, and Generation 6 really did it in with fairy types.
tl;dr 4 > 3 > 2 > 5 > 6 > 1